TEN LITTLE FINGERS - Arvind Gupta

Can you fill the empty bottle?Place a funnel in the neck ofan empty soda bottle. Packclay around the neck of thebottle so that there is nospace between the bottleand the funnel. Pour waterinto the funnel Notice whathappens. Then take the clayoff the bottle and funnel.The clay seals the neck ofthe bottle outside of thefunnel. When water flowsinto the funnel, the aircannot escape, except bygoing through the watervery slowly. The air in thebottle takes space andprevents the water fromcoming in. When the clay isremoved the air can escape,and water flows in easily.FUN WITH WATERThe SiphonPlace a tall jar full of water on ahigh table and an empty jar ona lower chair. Fill a tube withwater and hold the water in bypinching both ends of the tubeor with a clothespin. Place oneend of the tube in the top andthe other end in the lower jar.Open the two ends. The waterwill flow as long as the level ofwater in one jar is lower thanthe level of water in the otherjar. The pull of gravity causeswater to flow from the tube andreduces the pressure within it(at B). The air pressure isgreater at A and water is forcedinto the tube.Try to use the siphon withoutfilling the tube. Does it work?How does a straw work?Mix a few drops of ink in half aglass of water. Place atransparent straw in the glasswith coloured water. Suck up alittle of the water into thestraw. Then hold your fingeracross the top of the strawand pull the straw out of theliquid. What happens? Thenremove your finger from thestraw. While your fingercovers the top of the straw,the liquid remains in the straw.When you remove the finger,the water flows out. Whenyou cover the straw with yourfinger you are lessening thepressure of air over the straw.The greater pressure of airunder the straw can hold theliquid inside the straw.Make an atomiserHow many coins will it hold?How to compress airPlace a jar or a glass in abasin. Fill the jar to thebrim with water. Drop in25 paise coins or paperpins, holding them fromtheir edges. You will seethat you can drop in asurprising number ofcoins into the jar beforethe water flows over.The explanation for thisis that there is almost anelastic rubber likemembrane on top of thewater surface. Thissurface tension permitsyou to heap the waterquite high before itbreaks and the waterruns over.Make a slit in a plastic straw about one-third from oneend. Bend the straw at the slit and place the shortsection in a glass of water. Make sure the slit is nomore than 0.5 cm above the surface of the water. Blowhard through the straw. You will see that water entersthe straw from the glass and comes out through the slitlike a spray.Hold a glass with its mouth down and push itinto a deep bowl or bucket of water. You will seethat the water enters the glass a little way. Nobubbles of air escape. The water forces the airinto a smaller space. The molecules of air areforced closer together.